Abstract:
This study assessed exposures to respirable dust and silica exposures during seven construction activities. One hundred and eleven personal breathing zone samples were collected. The samples were collected by either a standard nylon cyclone or real-time aerosol monitor, which also recorded one-minute respirable dust levels. The real-time monitoring results were adjusted to reflect a standard nylon cyclone because the standard nylon cyclone method is a standard practice for characterizing respirable dust. Subjects w ho wore the standard nylon cyclone were asked to fill out a task-card to characterize their activities throughout the workday. A researcher task-card was filled out to track the specific activities, tasks, controls, and work environment when the subject wore the real-time aerosol monitor. Regression models were developed from the real-time monitoring data to predict exposure levels by activity with the parameters of task, controls and environmental conditions to determine where control strategies and technologies would be the most beneficial. Activities and tasks associated with the highest respirable dust and silica exposure levels were those involving grinding. Geometric means for respirable dust for surface and tuck-point grinding was 6.04 mg/m3 (3.19) and 2.25 mg/m3 (2.10), respectively. Exposure levels for respirable silica were 0.60 mg/m3 (4.33) for surface grinding and 0.21 mg/m3 (2.38) for tuck-point grinding. The regression model results indicated when local exhaust ventilation is applied exposure levels are substantially reduced. Predicted exposure levels for floor grinding were 1.43 mg/m3 (without controls) and 0.56mg/m3 (with local exhaust ventilation).